The present invention is related to Japanese patent application No. Hei. 11-333125, filed Nov. 24, 1999; the contents of which are incorporated herein by reference.
The present invention relates to an electro-mechanical impact detecting device, and more particularily, to an acceleration detecting device or collision detecting device suitable for a vehicle occupant protection system, vehicle air-bag system or seat-belt pretensioner.
A conventional electro-mechanical impact detecting device or collision detecting device is disclosed in JP-A No. Hei-9-306311. This device has a rotor with a weight positioned eccentric from the rotation shaft of the rotor. This device senses a vehicle collision when the rotor has rotated by a prescribed rotation value due to the eccentric mass of the weight. This means that the collision detecting device has its collision detection level corresponding to the prescribed rotation value of the rotor, and accordingly the device has a single detection level. This device produces a detection signal at a single impact level. However, when multi-stage control of the air-bag system is implemented, the dilating speed during an irregular collision rises. Without multi-stage control of the air-bag system, the system is incapable of timely air bag dilation, depending on the delay of collision detecting during irregular collision.
Accordingly, the present invention overcomes the aforementioned drawbacks by providing an electro-mechanical impact detecting device for a vehicle which uses multiple impact levels to detect impact acting on the vehicle. As a result, multi-stage control is used for the occupant protection system and collision detection is based on improved operational delay characteristics of the occupant protection system during an irregular collision.
In one aspect of the invention, a displacement member deviates in position by a exerting means force responsive to an impact acting on a vehicle. The present invention includes switches which close circuits sequentially at displacement values of the displacement member corresponding to at least a first and second impact levels of impact. The device detects at least a first and second impact level in response to closing the switches.
The switches trip to detect the first and second impact levels. The present invention has at least two impact levels sensed and, by using the operational time difference between the first impact level and second impact level and splitting the control domain into an ON part if the time difference is within a prescribed time length and an OFF part if it exceeds the time length, the air bag is dilated without delay. Moreover, by setting two or more prescribed time lengths, the collision can be divided into more divisions, e.g., OFF/Lo/Hi or OFF/Lo/Mid/Hi.
In another aspect of the invention, a rotating member rotates about a center of rotation. The rotating member has a center of mass which is eccentric from the rotation center, and rotates about the rotation center against an exertion force of exerting means in response to an impact on the vehicle. Switches close circuits sequentially at rotation values of the rotating member corresponding to at least first and second impact levels, and the device detects at least the first and second impact levels in response to the closing switches.
In another aspect of the invention, a displacement member is supported to deviate in the axial direction against an exertion force of exerting means in response to impact. Also, switches are provided which close circuits sequentially at axial displacement values of the displacement member corresponding to at least a first and second impact levels of impact. The impact detecting device detects at least the first and second impact levels in response to the switches closing.
In another aspect of the invention, the exerting means includes a first spring which exerts a force on the rotating member toward an initial rotation position. At least one or more second springs exert forces simultaneously or sequentially on the rotating member against rotation after the rotating member has rotated by a certain amount against the force of the first spring.
In another aspect of the invention, the exerting means includes a first spring which exerts a force on the displacement member toward an initial axial displacement position. At least one second spring exerts forces simultaneously or sequentially on the displacement member against the displacement thereof after the displacement member has deviated by a certain displacement against the exertion force of the first spring.
In another aspect of the invention, the impact detecting device includes a cam provided on the rotating member concentrically with the rotation center and adapted to rotate integrally with the rotating member in response to impact. The switches include fixed contacts and flat-spring moving contacts which are in contact with the surface of the cam. The switches are pushed and bent as the cam rotates and contacts the fixed contacts to close the circuits. At the contact surface, the cam surface is shaped such that the cam does not increase the bending value of the moving contacts.
In another aspect of the present invention, at least the first or second springs works also as the flat-spring moving contact. This reduces component parts. In another aspect, an exerting means comprises flat exerting springs which extend from a root section toward the cam and align in the direction of push of the cam. The exerting flat springs have no spacing at their root section from each other.
This eliminates contact movement during contact between the flat exerting springs. Consequently, the creation of frictional force between the flat exerting springs is eliminated and the operational fluctuation of the impact detecting device can be reduced.
In another aspect, an auxiliary rotor is located concentrically with the rotation center of the rotating member, and the second spring comprises a plurality of springs. One of the second springs is a torsional spring located concentrically with the rotation center of the rotating member. The torsional spring has one end fixed to a stationary member and another end fixed to part of the auxiliary rotor. The torsional spring exerts a force on the rotating member through the auxiliary rotor against the rotation of the rotating member. When an exertion force of the torsional spring of the rotating member is imposed, the torsional spring has another end that twists and prevents increase of operational fluctuation of the impact detecting device.
In another aspect, the impact detecting device includes a cam provided on the rotating member concentric with the rotation center and rotates integral with the rotating member in response to impact. The switches include fixed contacts and flat-spring moving contacts in contact with the surface of the cam. The switches are pushed and bent as the cam rotates and contact the fixed contacts to close the circuits. The switches have equal spacing between the fixed contacts and moving contacts. The cam contact surface is formed to shift in position along the rotation direction of the cam. This prevents the flat-spring contacts from being damaged by chattering or exceeding the spring stress limit.
In another aspect, the present invention includes a detection signal generation means that generates detection signals in response to closing of the switches at stepped values which match with at least the first and second impact levels. In another aspect, the second impact level is set greater than the first level. The detection signal generation means includes first and second electrical load elements, and is an electrical closing circuit having a closed switch at the first impact level and the first electrical load element, and another closing circuit having a closed switch at the second impact level and the first and second electrical load elements.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.